A motor-driven curtain rail in which a curtain, such as a curtain of the type referred to above, is opened and closed in accordance with a command from a switch operation or the like, has been known. In such a motor-driven curtain rail, a cable for operating a curtain is incorporated in a curtain rail disposed, e.g., on a ceiling so that that cable is driven by a motor to be fed out or wound on a reel, thereby opening or closing the curtain. Further, a motor-driven curtain rail with use for a very small curtain such as an interior curtain of a car or the like, in which a curtain is directly driven by a linear DC motor incorporated in a curtain rail so as to be opened or closed, has recently been produced and marketed.
In such a conventional motor-driven curtain rail using a cable, however, the whole curtain rail is large and heavy because it is necessary to mount a motor, a cable reel, a braking mechanism, and the like, on a curtain rail body. In the motor-driven curtain rail using a cable, there have been further disadvantages in that maintenance of the cable is troublesome due to faults such as cutting, entanglement, or the like, which are apt to occur in the cable in use. Further, the curtain cannot be freely opened by hand because the curtain is mechanically transmission-coupled with the driving motor through the cable.
In a motor-driven curtain rail utilizing a linear DC motor, on the other hand, the cost of the curtain rail is high because it is necessary to provide expensive permanent magnet elements of, for example, a ferrite material or the like, along the curtain rail over the entire length thereof. Further, there is a functional problem with this curtain rail because a linear DC motor per se has no braking function and the running speed thereof varies in accordance with load fluctuations.